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1
Fürstner, Alois, Denis N. Jumbam et Nongyuan Shi. « Synthesis of Coumarins and Quinolones by Intramolecular Aldol Condensation Reactions of Titanium Enediolates ». Zeitschrift für Naturforschung B 50, no 3 (1 mars 1995) : 326–32. http://dx.doi.org/10.1515/znb-1995-0304.
Texte intégralRésumé :
Low-valent titanium prepared by the reduction of TiCl3 with zinc dust oxidatively adds to α-ketoamides or α-ketoesters with the formation of the corresponding titanium enediolates. These 1,2-difunctional nucleophiles, which have hardly been used in organic synthesis so far, undergo regioselective intramolecular aldol condensation reactions with various electrophiles such as aldehydes, ketones, nitriles, esters and amides. This methodology allows the synthesis of differently substituted coumarin and 2-quinolone derivatives.
2
Kagayama, Akifumi, Koji Igarashi et Teruaki Mukaiyama. « Efficient method for the preparation of pinacols derived from aromatic and aliphatic ketones by using low-valent titanium reagents in dichloromethane-pivalonitrile ». Canadian Journal of Chemistry 78, no 6 (1 juin 2000) : 657–65. http://dx.doi.org/10.1139/v00-010.
Texte intégralRésumé :
The reductive coupling reaction of aldehydes and ketones, including unsymmetrical aliphatic ketones, proceeded smoothly to give the corresponding pinacols in good to high yields under mild conditions by using combination of titanium(II) chloride and zinc or titanium(IV) chloride and zinc in dichloromethane-pivalonitrile. Meso-selective formation of the coupling products was observed in the cases of some aliphatic ketones. The diastereoselectivities of coupling products depend on both difference of bulkiness of 2-, and 2'-substituents of carbonyl group of the reactant, and overall steric effect around the carbonyl groups.Key words: diastereoselective pinacol reaction, dichloromethane-pivalonitrile, titanium(II) chloride, titanium(IV) chloride, zinc.
3
Silwamba, Marthias, Mayumi Ito, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Ryota Hashizume, Tomoki Fukushima, Ilhwan Park et al. « Recovery of Lead and Zinc from Zinc Plant Leach Residues by Concurrent Dissolution-Cementation Using Zero-Valent Aluminum in Chloride Medium ». Metals 10, no 4 (20 avril 2020) : 531. http://dx.doi.org/10.3390/met10040531.
Texte intégralRésumé :
Zinc plant leach residues (ZPLRs) contain significant amounts of metal compounds of lead (Pb), zinc (Zn), iron (Fe), etc., hence, they are considered as a secondary source of metals. On the other hand, ZPLRs are regarded as hazardous materials because they contain heavy metals that pollute the environment. Resources and environmental concerns of ZPLRs were addressed in this study by removing/recovering Pb and Zn using a concurrent dissolution and cementation technique. To cement the dissolved Pb and Zn in leaching pulp, zero-valent aluminum (ZVAl) was added during ZPLRs leaching in the hydrochloric (HCl)–sodium chloride (NaCl) solution. The resulting cemented metals were agglomerated and separated by sieving. Lead removal increased with increasing both NaCl and HCl concentrations. However, when ZVAl was added, significant Pb removal was achieved at a low concentration. Zinc was not cemented out of the pulp using ZVAl and its recovery from ZPLRs was dependent on the HCl concentration only. By applying a concurrent dissolution and cementation technique, both Pb and Zn were removed using a low concentration of NaCl, and most importantly Pb—the most toxic metal in ZPLRs—was captured and separated before the solid-liquid separation, hence, eliminating the need for extensive washing of the generated residues to remove the inherent residual solution.
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Kantlehner, Willi, Reiner Aichholz et Martin Karl. « Orthoamide und Iminiumsalze, LXXIV [1]. Umsetzung von N,N,N´,N´-Tetramethyl-chlorformamidiniumchlorid mit Metallen ». Zeitschrift für Naturforschung B 67, no 4 (1 avril 2012) : 305–19. http://dx.doi.org/10.1515/znb-2012-0404.
Texte intégralRésumé :
N,N,N’,N’-Tetramethyl-formamidinium chloride (2a) reacts with elemental sodium in various solvents to give N,N,N’,N’,N’’,N’’-hexamethyl-guanidinium chloride (4a). The reaction of 2a with potassium affords N,N,N’,N’,N’’,N’’,N’’’,N’’’-octamethyl-oxamidinium dichloride (3a). From the reaction of 2a with magnesium in different solvents in general result mixtures of the salts 4a, 3a and N,N,N’,N’-tetramethyl-formamidinium chloride (10a). The composition of these mixtures depends on the solvent and the reaction temperature. Similar results are obtained, when a zinc/copper couple is used instead of magnesium. Very likely from 2a and magnesium or zinc, respectively, organometallic intermediates 11, 12 are formed which could be trapped by aromatic aldehydes and phenylisocyanate. The salt 2a can be reductively coupled by a low-valent titanium reagent to give the oxamidinium salt 3a.
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Guo, Jing, Le Zhu, Na Sun et Yeqing Lan. « Degradation of nitrobenzene by sodium persulfate activated with zero-valent zinc in the presence of low frequency ultrasound ». Journal of the Taiwan Institute of Chemical Engineers 78 (septembre 2017) : 137–43. http://dx.doi.org/10.1016/j.jtice.2017.04.045.
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Aleksandrova, Mariya, Tatyana Ivanova, Velichka Strijkova, Tsvetozar Tsanev, Ajaya Kumar Singh, Jai Singh et Kostadinka Gesheva. « Ga-Doped ZnO Coating—A Suitable Tool for Tuning the Electrode Properties in the Solar Cells with CdS/ZnS Core-Shell Quantum Dots ». Crystals 11, no 2 (29 janvier 2021) : 137. http://dx.doi.org/10.3390/cryst11020137.
Texte intégralRésumé :
Two layer system from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO, GZO) were studied for transparency in the visible electromagnetic range, reflectivity in the near infrared range, conductivity and valent band for a solar cells with quantum dots. The bi-layer coatings produced at optimized oxygen partial pressure, films thickness and surface roughness exhibit improved optical properties without worsening the electrical parameters, even if additional oxygen introduction during the reactive sputtering of the GZO. With an average optical transmittance of 91.3% in the visible range, average reflection and resistivity lower than 0.4 × 10−2 Ω.cm, these coatings are suitable for top electrode in the solar cells. The obtained results reveal that multilayered stacks of transparent ITO/Ga-doped ZnO coatings possess relatively low surface roughness (7–9 nm) and appropriate refractive index. The additional oxidation of GZO films induces modification of the film thickness and respectively of their optical performances.
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Jeon, Sanghee, Sharrydon Bright, Ilhwan Park, Carlito Baltazar Tabelin, Mayumi Ito et Naoki Hiroyoshi. « The Effects of Coexisting Copper, Iron, Cobalt, Nickel, and Zinc Ions on Gold Recovery by Enhanced Cementation via Galvanic Interactions between Zero-Valent Aluminum and Activated Carbon in Ammonium Thiosulfate Systems ». Metals 11, no 9 (27 août 2021) : 1352. http://dx.doi.org/10.3390/met11091352.
Texte intégralRésumé :
The use of galvanic interactions between zero-valent aluminum (ZVAl) and activated carbon (AC) to recover gold (Au) ions is a promising technique to overcome the challenges due to the poor recovery in ammonium thiosulfate systems, but the applicability to practical Au ore processing remains elusive so far. The present study describes (1) the recovery of Au ions from low Au concentrations, which are typical concentrations used in Au ore processing; and (2) an investigation into the effects of various coexisting base metal ions that can be present in pregnant ore-leached solutions. The results showed that high Au recovery (i.e., over 85%) was obtained even at low Au concentrations under the following conditions: 1:1 of 0.15 g of ZVAl and AC with 10 mL of ammonium thiosulfate solution containing 5 mg/L of Au ions at 25 °C for 1 h in an anoxic atmosphere. Selected coexisting metal ions (i.e., copper, iron, cobalt, nickel, and zinc) were studied to establish their effects on Au recovery, and the results showed that the Au recovery was enhanced (about 90%) when copper ions coexist in the solution with minimal effects from other competing base metal ions.
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Duan, Qiaohui, et Qiaohui Duan. « Facile Electrode Additive Stabilizes Structure of Electrolytic MnO2 for Mild Aqueous Rechargeable Zinc-Ion Battery ». ECS Meeting Abstracts MA2022-01, no 4 (7 juillet 2022) : 562. http://dx.doi.org/10.1149/ma2022-014562mtgabs.
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Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted much attention recently due to the high abundance, low cost, high theoretical capacity up to 820 mAh g-1 with multi-valent charge carrier, and compatibility with aqueous electrolyte of the zinc anode.[1] Especially, the introduction of neutral or mild acidic electrolyte greatly improves the reversibility of zinc anode compared to conventional alkaline ZIBs.[2] Among all the cathode candidates, MnO2 is most attractive due to its relatively high energy density, low toxicity and low cost.[3] However, MnO2 electrode suffers from capacity fading during cycling mainly due to Mn dissolution and structural change. The addition of Mn2+ into the mild acidic electrolyte is a common method to suppress Mn dissolution.[4] Other strategies like structural design and surface coatings are also developed to suppress Mn dissolution.[5, 6] Though the cycle performance still cannot meet the demand of application, as the irreversible formation of inactive ZnMn2O4 during cycles still requires to be tackled. Here, we proposed Bi2O3 as a facile electrode additive in the electrode to suppress ZnMn2O4 formation and improve the cyclability of commercial electrolytic manganese dioxide (EMD). XRD, in-situ pH measurements and ICP tests suggest that inactive ZnMn2O4 is formed upon cycling due to the interaction between MnO2 and zincate ions in the electrolyte from localized increase in pH, and Bi2O3 dissolves into the electrolyte in the presence of zincate ions and forms a complex with the zincate ions to suppress the reaction pathway. A high capacity of 269 mAh g-1 is maintained at 100 mA g-1 after 50 cycles with a capacity retention of 91.5% when EMD with 10 wt% of Bi2O3 is tested in ZnSO4 electrolyte without Mn2+ additive. Combining both Bi2O3 electrode additive and Mn2+ electrolyte additive, EMD can maintain a stable capacity of 190 mAh g-1 for 1000 cycles at 1000 mA g-1 (about 3.3C). More characterizations are underway to further understand the role of Bi2O3 and the results will be shown during the meeting. Reference: [1] B. Tang, L. Shan, S. Liang, J. Zhou, Issues and opportunities facing aqueous zinc-ion batteries, Energy & Environmental Science, 12 (2019) 3288-3304. [2] J. Hao, X. Li, X. Zeng, D. Li, J. Mao, Z. Guo, Deeply understanding the Zn anode behaviour and corresponding improvement strategies in different aqueous Zn-based batteries, Energy & Environmental Science, 13 (2020) 3917-3949. [3] N. Zhang, X. Chen, M. Yu, Z. Niu, F. Cheng, J. Chen, Materials chemistry for rechargeable zinc-ion batteries, Chemical Society Reviews, 49 (2020) 4203-4219. [4] H. Pan, Y. Shao, P. Yan, Y. Cheng, K.S. Han, Z. Nie, C. Wang, J. Yang, X. Li, P. Bhattacharya, Reversible aqueous zinc/manganese oxide energy storage from conversion reactions, Nature Energy, 1 (2016) 1-7. [5] J. Huang, Z. Wang, M. Hou, X. Dong, Y. Liu, Y. Wang, Y. Xia, Polyaniline-intercalated manganese dioxide nanolayers as a high-performance cathode material for an aqueous zinc-ion battery, Nature communications, 9 (2018) 1-8. [6] B. Wu, G. Zhang, M. Yan, T. Xiong, P. He, L. He, X. Xu, L. Mai, Graphene scroll‐coated α‐MnO2 nanowires as high‐performance cathode materials for aqueous Zn‐ion battery, Small, 14 (2018) 1703850. Figure 1
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Bondarieva, Antonina, et Viktoriia Tobilko. « Obtaining and study of physical-chemical properties of porous materials based on kaolin ». Technology audit and production reserves 3, no 3(71) (29 juin 2023) : 30–34. http://dx.doi.org/10.15587/2706-5448.2023.283177.
Texte intégralRésumé :
The object of research is kaolin from the Hlukhovetsky deposit (Ukraine). On its basis, granulated sorbent materials were obtained with the addition of various amounts of cellulose as a pore former. After forming the samples, they were dried and fired at a temperature of 800 °C. The obtained granules with a size of 8–9 mm were modified with zero-valent iron. The physicochemical, including sorption properties of granular composites were studied. Using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), the morphology of the obtained samples was investigated and the presence of zero-valent iron particles on the surface and in the pores of the sorbents was confirmed. Based on desorption experiments, it was determined by chemical analysis that the Fe0 content in modified samples with increased pore former content increases from 0.01 g/g of granules for a sample containing 1% cellulose to 0.016 g/g for a carrier with 3 % pore former. The specific surface area and pore volume of the samples were determined by the method of low-temperature adsorption-desorption of nitrogen. Thus, with an increase in the content of the pore former in the ceramic mass, the specific surface of both unmodified and modified samples slightly decreases. Thus, with a cellulose content of 1 %, it is 20 m2/g and 17 m2/g, respectively. When the pore former is increased to 3%, these values are 15 m2/g and 12 m2/g. After applying a layer of zero-valent iron on porous granules, the volume of pores decreases, which is due to the formation of agglomerates of iron particles during synthesis. The study of the sorption capacity of the obtained sorbents with respect to Cr(VI) from model solutions containing a mixture of metal cations (copper, cadmium, cobalt, zinc) showed that granular materials exhibit sorption capacity for metal anions, even in the presence of cations. The amount of chromium sorption naturally increases for modified samples with an increase in the cellulose content in them. However, for model solutions that do not additionally contain metal cations, the sorption value is somewhat higher. Thus, for a sample with a 3 % pore former content, the sorption value is 0.7 mg/g and 0.9 mg/g, respectively, at an initial chromium(VI) concentration of 10 mg/g. The obtained experimental data indicate that the obtained porous granular sorbents based on kaolin can be used in the further treatment of wastewater from electroplating enterprises, which contain a mixture of pollutants in both anionic and cationic forms.
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Janes, Alar, Jaanus Eskusson, Paul-Egert Peensalu, Thomas Thomberg et Enn Lust. « A Low-Cost Zn-Ion Hybrid Supercapacitors with High Energy Density ». ECS Meeting Abstracts MA2024-02, no 6 (22 novembre 2024) : 761. https://doi.org/10.1149/ma2024-026761mtgabs.
Texte intégralRésumé :
In recent years, hybrid supercapacitors with greater potential and improved energy density have been completed by combining some battery and supercapacitor type electrodes. According to some researchers’ research, “hybrid” supercapacitor systems are technically “asymmetric” supercapacitor systems since they are built on two separate supercapacitor type electrodes. The primary aim behind the development of a hybrid capacitor (HC) is to improve the energy density or specific energy of the device, which will significantly boost the storage property. Moreover, the use of an electrical double layer capacitor type electrode provides a large surface area, improving the electrode/electrolyte interaction region, and helps in the fast ion-adsorption process, which prevents the degradation of the battery-type electrode due to repeated charge-discharge cycles. A suitable combination of specific power (due to the EDLC electrode) and specific energy (due to the faradic electrode) could drastically enhance the stability and longevity of the hybrid supercapacitor device. The di/tri-valent metal ion (Mg2+, Zn2+, Ca2+, Al3+, etc.) hybrid capacitors have garnered considerable attention in recent years owing to their potential cost benefit and application in stationary storage systems, whose development is crucial for the mass-scale penetration of renewable energy technologies. Zinc‐ion hybrid supercapacitors (ZIHSs) may be the most promising energy storage device alternatives for portable and large‐scale electronic devices, as they combine the benefits of both supercapacitors and zinc‐ion batteries. ZIHSs are mostly based on battery-type Zn metal as an anode and physical adsorption-based carbon materials as the cathode. Porous carbon materials with high surface area, good electrochemical stability, low cost, high electronic conductivity and tuneable surface structure are deemed as promising cathode materials for ZIHSs. It is generally recognized that the micropores facilitate electrochemical energy storage, and mesopores can effectively reduce the ion diffusion distance and transport resistance. Therefore, the adjustment and optimization of porous carbons electrodes are of great significance to ZIHSs. This work provides some insight into the strategy for designing effective non-aqueous and aqueous Zn-ion hybrid supercapacitors. Electrochemical characteristics of Zn-ion hybrid supercapacitor cells based on non-aqueous 1 M acetonitrile (AN) or propylene carbonate (PC) electrolytes with addition Zn(BF4)2, zinc di[bis(trifluoromethylsulfonyl)imide] (Zn(TFSI)2) and zinc trifluoromethanesulfonate (Zn(OTf)2) have been studied. Very high energy and power densities (80 Wh kg−1 and 21.2 kW kg−1) have been measured for 1 M Zn(BF4)2/AN based Zn-ion based hybrid supercapacitors (Fig. 1a). Very good stability during 3,000 cycles of cells has been achieved demonstrating reasonably high energy efficiency value (66.8%) for Zn(TFSI)2/AN based ZIHS cell, decreasing in the order of electrolytes: Zn(TFSI)2/AN > Zn(BF4)2/PC > Zn(TFSI)2/PC > Zn(OTf)2/AN > Zn(BF4)2/AN. Some assembled ZIHSs had shown excellent cycling and energy stability over 20,000 cycles [1]. Electrochemical behaviour of Zn cation based salts in various aqueous electrolytes (ZnSO4, Zn(BF4)2, Zn(TFSI)2, and Zn(OTf)2) has been studied in thin ZIHS cell and compared with Zn(ClO4)2 aqueous electrolyte based cell electrochemical characteristics. At moderate specific power value (10 kW kg− 1) noticeable decrease of specific energy has been established in the order of aqueous electrolytes: Zn(ClO4)2 ⩾ Zn(BF4)2 > Zn(OTf)2 > Zn(TFSI)2 > ZnSO4 (Fig. 1b). The stability of Zn-ion hybrid supercapacitor cells under study in aqueous electrolyte solutions has been tested using the long lasting (up to 10,000 cycles) constant current charge/discharge method and very good stability for Zn(OTf)2, Zn(ClO4)2 and ZnSO4 has been observed [2,3]. Taking into account the cheap and environmental friendliness electrodes and electrolyte used, the results can be applied for assembling of the cheap high energy density hybrid supercapacitors for sustainable energy storage/recuperation complexes, combined with photovoltaic fields and/or wind electricity generating systems. Acknowledgements This work was supported by the Estonian Ministry of Education and Research (TK210, Centre of Excellence in Sustainable Green Hydrogen and Energy Technologies), Personal Research Grant PRG676 and R&D project EAG228. The experimental part of the research was partially co-funded by the Feasibility Fund of the University of Tartu Development Fund. References [1] K.-S. Põder, J. Eskusson, E. Lust, and A. Jänes, J. Electrochem. Soc. 170, 060501, 2023. [2] J. Eskusson, T. Thomberg, E. Lust, and A. Jänes, J. Electrochem. Soc. 169,020512, 2022. [3] J. Eskusson, T. Thomberg, T. Romann, K. Lust, E. Lust, and A. Jänes, J. Solid State Electrochem. 25, 2869, 2021. Figure 1
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Kulesza, Pawel J., et Iwona A. Rutkowska. « (Invited) Homo- and Heteromatallic Cyanide Bridged Networks and Derived Materials for Selected Electrochemical Applications Involving Enhanced Charge Transport and Storage ». ECS Meeting Abstracts MA2022-02, no 59 (9 octobre 2022) : 2207. http://dx.doi.org/10.1149/ma2022-02592207mtgabs.
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Hexacyanoferrates and related cyanometallates exhibit model electron transfer properties that are of importance to many electrochemical and related applications. In particular homo- and heterometallic cyanide bridged networks and derived materials have proven to exhibit very rich and diverse electrochemical properties. Their redox properties can be tuned by adjusting stoichiometry and oxidation state of the constituent metal centers, incorporation of interstitial ions, or preparation methods. Polynuclear cyanometallates are promising open-framework systems for low-cost electrochemical energy storage applications. Both soluble and insoluble analogues of Prussian blue have been explored as cathode materials with lithium, sodium, potassium, magnesium, calcium, and even zinc intercalated ionic carriers. Electrochromic devices are another promising area for employing the unique properties of cyanometallates. Prussian blue itself exhibits electrocatalytic properties toward hydrogen peroxide, and it has been used for biosensing and amperometric detection of glucose, L-cysteine, and glutamate. Also removal of radioactive cesium ions from contaminated water has been successfully achieved with Prussian blue and its metal substituted analogues. It is well-established that the choice of redox-active charge-storage material has a significant impact on the performance of a redox flow battery. The concentration of redox centers and their reaction kinetics have an influence on the available current densities and, thus, the power of the device. Remembering the requirement of good solubility of redox species, the semi-solid slurry approach (provided that the dispersion is homogeneous) represents another effective way to improve the volumetric capacity of the redox electrolyte (i.e. of the electrolyte with dissolved redox couples). An interesting approach to improve current densities involves application of circulating suspensions of electroactive materials. Prussian blue and its metal (Fe, Co, Ni, etc.) substituted analogues, which are electroactive mixed-valence inorganic systems, exhibit very rich and diverse electrochemistry. Their electrochemical properties that can be tuned through the variation of the material composition. Special attention will be paid to the formation of stable colloidal suspensions of truly mixed-valence fast-conducting Berlin Green, iron(III) hexacyanoferrate(III,II), together with multi-layered clay-like nickel(II) hexacyanoferrate(III) structures characterized by fast potassium counter-cation motion. It can be hypothesized that the proposed system could serve as the catholyte redox suspension containing large population of mixed-valence redox centers and capable of fast charge propagation and, consequently, yielding fairly large current densities. The materials can also be explored for sorption of large concentrations of Zn2+ ions and for the improvement of the Zn2+/Zn chemistry. While the application of Zn2+/Zn as the anode active system is well established in redox flow batteries, we are going to address and minimize limitations that include the efficiency of zinc deposition and the hydrogen evolution reaction taking place at the potentials where Zn is electrodeposited. The increase of current density could be achieved not only by reducing the viscosity of the electrolyte, thus accelerating charge-carrier transport, but also – by referencing to our experience with mixed-valent nickel hexacyanoferrate system as charge relay for dye-sensitized solar cells – through improvement of the dynamics of charge propagation by improving mobility of charge compensating counter-ions.
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Li, Bo, Jing Zhong, Hao Wang, Jialun Gu, Fucong Lyu, Shengmei Chen, Haikun Wu et al. « Fluorine‐lodged high‐valent high‐entropy layered double hydroxide for efficient, long‐lasting zinc‐air batteries ». Angewandte Chemie International Edition, 17 septembre 2024. http://dx.doi.org/10.1002/anie.202410978.
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Efficient and stable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts are urgently needed to unlock the full potential of zinc‐air batteries (ZABs). High‐valence oxides (HVOs) and high entropy oxides (HEOs) are suitable candidates for their optimal electronic structures and stability but suffer from demanding synthesis. Here, a low‐cost fluorine‐lodged high‐valent high‐entropy layered double hydroxide (HV‐HE‐LDH) (FeCoNi2F4(OH)4) is conveniently prepared through multi‐ions co‐precipitation, where F‐ are firmly embedded into the individual hydroxide layers. Spectroscopic detections and theoretical simulations reveal high valent metal cations are obtained in FeCoNi2F4(OH)4, which enlarge the energy band overlap between metal 3d and O 2p, enhancing the electronic conductivity and charge transfer, thus affording high intrinsic OER catalytic activity. More importantly, the strengthened metal‐oxygen (M‐O) bonds and stable octahedral geometry (M‐O(F)6) in FeCoNi2F4(OH)4 prevent structural reorganization, rendering long‐term catalytic stability. Furthermore, an efficient three‐phase reaction interface with fast oxygen transportation was constructed, significantly improving the ORR activity. ZABs assembled with FeCoNi2F4(OH)4@HCC (hydrophobic carbon cloth) cathodes deliver a top performance with high round‐trip energy efficiency (60.6% at 10 mA cm‐2) and long‐term stability (efficiency remains at 58.8% after 1050 charge‐discharge cycles).
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Li, Bo, Jing Zhong, Hao Wang, Jialun Gu, Fucong Lyu, Shengmei Chen, Haikun Wu et al. « Fluorine‐lodged high‐valent high‐entropy layered double hydroxide for efficient, long‐lasting zinc‐air batteries ». Angewandte Chemie, 17 septembre 2024. http://dx.doi.org/10.1002/ange.202410978.
Texte intégralRésumé :
Efficient and stable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts are urgently needed to unlock the full potential of zinc‐air batteries (ZABs). High‐valence oxides (HVOs) and high entropy oxides (HEOs) are suitable candidates for their optimal electronic structures and stability but suffer from demanding synthesis. Here, a low‐cost fluorine‐lodged high‐valent high‐entropy layered double hydroxide (HV‐HE‐LDH) (FeCoNi2F4(OH)4) is conveniently prepared through multi‐ions co‐precipitation, where F‐ are firmly embedded into the individual hydroxide layers. Spectroscopic detections and theoretical simulations reveal high valent metal cations are obtained in FeCoNi2F4(OH)4, which enlarge the energy band overlap between metal 3d and O 2p, enhancing the electronic conductivity and charge transfer, thus affording high intrinsic OER catalytic activity. More importantly, the strengthened metal‐oxygen (M‐O) bonds and stable octahedral geometry (M‐O(F)6) in FeCoNi2F4(OH)4 prevent structural reorganization, rendering long‐term catalytic stability. Furthermore, an efficient three‐phase reaction interface with fast oxygen transportation was constructed, significantly improving the ORR activity. ZABs assembled with FeCoNi2F4(OH)4@HCC (hydrophobic carbon cloth) cathodes deliver a top performance with high round‐trip energy efficiency (60.6% at 10 mA cm‐2) and long‐term stability (efficiency remains at 58.8% after 1050 charge‐discharge cycles).
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Dankert, Fabian, et Eva Hevia. « Synthesis and Modular Reactivity of Low Valent Al/Zn Heterobimetallics Supported by Common Monodentate Amides ». Chemistry – A European Journal, 8 janvier 2024. http://dx.doi.org/10.1002/chem.202304336.
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Recent advances on low valent main group metal chemistry have shown the excellent potential of heterobimetallic complexes derived from Al(I) to promote cooperative small molecule activation processes. A signature feature of these complexes is the use of bulky chelating ligands which act as spectators providing kinetic stabilization to their highly reactive Al‐M bonds. Breaking new ground in this field, here we report the synthesis of novel unsupported Al/Zn bimetallics prepared by the selective formal insertion of AlCp* into the Zn‐N bond of the utility zinc amides ZnR2 (R = HMDS, hexamethyldisilazide; or TMP, 2,2,6,6‐tetramethylpiperidide). By systematically assessing the reactivity of the new [(R)(Cp*)AlZn(R)] bimetallics towards carbodiimides, structural and mechanistic insights have been gained on their ability to undergo insertion in their Zn‐Al bond. Disclosing a dramatic ligand effect, when R = TMP, an isomerization process can be induced giving [(TMP)2AlZn(Cp*)] which displays a special reactivity towards carbodiimides and carbon dioxide involving both its Al‐N bonds, leaving its Al‐Zn bond untouched.
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Feng, Da-Ming, Ying Sun, Zhong-Yong Yuan, Yang Fu, Baohua Jia, Hui Li et Tianyi Ma. « Ampoule method fabricated sulfur vacancy-rich N-doped ZnS electrodes for ammonia production in alkaline media ». Materials for Renewable and Sustainable Energy 10, no 2 (12 avril 2021). http://dx.doi.org/10.1007/s40243-021-00193-x.
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AbstractThe electrochemical production of green and low-cost ammonia requests the development of high-performance electrocatalysts. In this work, the ampoule method was applied to modulate the surface of the zinc electrode by implanting defects and low-valent active sites. The N-doped ZnS electrocatalyst was thus generated by sulfurization with thiourea and applied for electrocatalytic nitrogen reduction reaction (ENRR). Given the rich sulfur vacancies and abundant Zn-N active sites on the surface, excellent catalytic activity and selectivity were obtained, with an NH3 yield rate of 2.42 × 10–10 mol s−1 cm−2 and a Faradaic efficiency of 7.92% at − 0.6 V vs. RHE in 0.1 M KOH solution. Moreover, the as-synthesized zinc electrode exhibits high stability after five recycling tests and a 24 h potentiostatic test. The comparison with Zn foil, non-doping ZnS/Zn and recent metal sulfide electrocatalysts further demonstrated advanced catalytic performance of N@ZnS/Zn for ENRR. By simple synthesis, S vacancies, and N-doping defects, this promising electrocatalyst would represent a good addition to the arena of transition-metal-based catalysts with superior performance in ENRR. Graphic abstract
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Zhang, Haiyuan, Yun Wang, Jiahua Zhu, Xiaohua Lu, Yang Bai, Wei Li et Liwen Mu. « A new approach for methane oxidation : photocatalytic ozonation over noble metal decorated zinc oxide nanocatalysts ». Chemical Synthesis 4, no 4 (12 décembre 2024). https://doi.org/10.20517/cs.2024.116.
Texte intégralRésumé :
We designed a new approach to oxidize methane, a potent greenhouse gas. In this approach, the synergistic effect of photocatalytic ozonation is utilized to oxidize methane at low concentrations. Using ZnO nanomaterials modified with noble metals (i.e., Au, Pt, and Pd), results show that the catalytic oxidation of methane is generally significantly improved by the synergistic system approach. More specifically, the efficiency of photocatalytic ozonation was at least two times higher than the sum of the contributions from individual sub-processes (i.e., photocatalysis, catalytic ozonation, and ozone photolysis), and the synergistic effect was effectively utilized. The durability of the catalysts is another highlight, with no decrease in activity over ten cycles. Based on the experimental results, combined with the characterization, and taking Au/ZnO as an example, it can be seen that Au/ZnO with high specific surface area and high adsorption capacity is more conducive to ozone adsorption and activation, enhances the formation of active radicals (·O2- and 1O2) and promotes the synergistic effect. Meanwhile, we believe that the larger Au nanoclusters and the zero-valent stabilized Au are important reasons for the durability of the catalyst. This work provides a novel approach to removing low-concentration methane and guides further development of a practical photocatalytic ozonation system.
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Inoue, Katsutoshi. « Adsorptive Removal of Phosphorus using Metal-Loaded Biosorbents from Aquatic Environment ». Juniper Online Journal Material Science 4, no 2 (23 février 2018). http://dx.doi.org/10.19080/jojms.2018.04.555632.
Texte intégralRésumé :
Adsorption gel for metal ions was prepared from orange juice residue in a simple manner by interacting with calcium hydroxide. Heavy metal ions such as lead(II), iron(III) and copper(II) were selectively adsorbed over other metal ions such as zinc(II), cadmium(II) and manganese(II) at low pH. Loading this gel with high valent metal ions such as lanthanum(III), cerium(III) and zirconium(IV) resulted in effective and selective adsorption of phosphate from water containing excess concentrations of other anionic species such as sulfate, carbonate and chloride. Zirconium(IV) was the most effective among the metal ions. Among the phosphorus compounds, phosphate was more strongly adsorbed on zirconium(IV)-loaded gel than phosphite and hypophosphite. The adsorption capacity for phosphate on the zirconium(IV)-loaded gel was the highest among adsorbents that have been reported in literature, including other zirconium(IV)-containing adsorbents. The effectiveness of this gel was verified by applying it to actual wastewater samples containing trace concentrations of phosphorus.
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Luo, Xu, Dali Yang, Xiaoqian He, Shengchun Wang, Dongchao Zhang, Jiaxin Xu, Chih-Wen Pao et al. « Valve turning towards on-cycle in cobalt-catalyzed Negishi-type cross-coupling ». Nature Communications 14, no 1 (2 août 2023). http://dx.doi.org/10.1038/s41467-023-40269-y.
Texte intégralRésumé :
AbstractLigands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoCl2bpy2 catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies. The solvent and ligand were found to be essential for the generation of catalytic active Co(I) species, among which acetonitrile and bipyridine ligand are resistant to the disproportionation events of Co(I). Investigations, based on Quick-X-Ray Absorption Fine Structure (Q-XAFS) spectroscopy, Electron Paramagnetic Resonance (EPR), IR allied with DFT calculations, allow comprehensive mechanistic insights that establish the structural information of the catalytic active cobalt species along with the whole catalytic Co(I)/Co(III) cycle. Moreover, the acetonitrile and bipyridine system can be further extended to the acylation, allylation, and benzylation of aryl zinc reagents, which present a broad substrate scope with a catalytic amount of Co salt. Overall, this work provides a basic mechanistic perspective for designing cobalt-catalyzed cross-coupling reactions.
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Migliore, Eleonora, Vivian K. Amaitsa, Francis M. Mutuku, Indu J. Malhotra, Dunstan Mukoko, Anika Sharma, Prathik Kalva, Amrik S. Kang, Charles H. King et A. Desiree LaBeaud. « Dietary Intake and Pneumococcal Vaccine Response Among Children (5–7 Years) in Msambweni Division, Kwale County, Kenya ». Frontiers in Nutrition 9 (23 mai 2022). http://dx.doi.org/10.3389/fnut.2022.830294.
Texte intégralRésumé :
BackgroundVaccine and sufficient food availability are key factors for reducing pneumonia outbreaks in sub-Saharan Africa.MethodsIn this study, the 10-valent pneumococcal conjugate vaccine (Synflorix® or PCV10) was administered to a child cohort (5–7 years old, n = 237) in Msambweni, Kenya, to determine relationships between dietary intake, nutritional/socioeconomic status of mothers/caregivers, and vaccine response. 7-day food frequency questionnaire (FFQ), dietary diversity score (DDS) and single 24-h dietary recall were used to address participants' dietary assessment and nutritional status. Individual food varieties were recorded and divided into 9 food groups as recommended by Food and Agriculture Organization. Anthropometric measurements, nasopharyngeal swabs and vaccine administration were performed at the initial visit. Participants were followed 4–8 weeks with a blood draw for pneumococcal IgG titers assessed by Luminex assay.FindingsChronic malnutrition was prevalent in the cohort (15% stunting, 16% underweight). Unbalanced dietary intake was observed, with mean energy intake 14% below Recommended Dietary Allowances (1,822 Kcal) for 5–7 years age range. 72% of the daily energy was derived from carbohydrates, 18% from fats and only 10% from proteins. Poor anthropometric status (stunting/underweight) was associated with low socioeconomic/educational status and younger mother/caregiver age (p < 0.002). Limited intake of essential micronutrients (vitamins A, E, K) and minerals (calcium, potassium) associated with low consumption of fresh fruits, vegetables, and animal source foods (dairy, meat) was observed and correlated with poor vaccine response (p < 0.001). In contrast, children who consumed higher amounts of dietary fiber, vitamin B1, zinc, iron, and magnesium had adequate vaccine response (p < 0.05). Correlation between higher dietary diversity score (DDS), higher Vitamin E, K, Zinc intake and adequate vaccine response was also observed (p < 0.03).InterpretationOverall, this study highlights ongoing food scarcity and malnutrition in Kenya and demonstrates the links between adequate socioeconomic conditions, adequate nutrient intake, and vaccine efficacy.
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Lee, Yeryeong, Jayaraman Theerthagiri, Nuttapon Yodsin, Ahreum Min, Cheol Joo Moon, Siriporn Jungsuttiwong et Myong Yong Choi. « Mitigating Intraphase Catalytic‐Domain Transfer via CO2 Laser for Enhanced Nitrate‐to‐Ammonia Electroconversion and Zn‐Nitrate Battery Behavior ». Angewandte Chemie, 13 août 2024. http://dx.doi.org/10.1002/ange.202413774.
Texte intégralRésumé :
Developing sustainable energy solutions is critical for addressing the dual challenges of energy demand and environmental impact. In this study, a zinc‐nitrate (Zn‐NO3−) battery system was designed for the simultaneous production of ammonia (NH3) via the electrocatalytic NO3− reduction reaction (NO3RR) and electricity generation. Continuous wave CO2 laser irradiation yielded precisely controlled CoFe2O4@nitrogen‐doped carbon (CoFe2O4@NC) hollow nanocubes from CoFe Prussian blue analogs (CoFe‐PBA) as the integral electrocatalyst for NO3RR in 1.0‐M KOH, achieving a remarkable NH3 production rate of 10.9 mgh−1cm−2 at −0.47 V versus RHE with exceptional stability. In‐situ and ex‐situ methods revealed that the CoFe2O4@NC surface transformed into high‐valent Fe/CoOOH active‐species, optimizing the adsorption energy of NO3RR (*NO2 and *NO species) intermediates. Furthermore, DFT calculations validated the possible NO3RR pathway on CoFe2O4@NC starting with NO3− conversion to *NO2 intermediates, followed by reduction to *NO. Subsequent protonation forms the *NH and *NH2 species, leading to NH3 formation via final protonation. The Zn‐NO3− battery utilizing the CoFe2O4@NC cathode exhibits dual functionality by generating electricity with a stable open‐circuit voltage of 1.38‐V versus Zn/Zn2+ and producing NH3. This study inspires the simple design of low‐cost catalysts for NO3RR‐to‐NH3 conversion and positions the Zn‐NO3− battery as a promising technology for industrial applications.
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Lee, Yeryeong, Jayaraman Theerthagiri, Nuttapon Yodsin, Ahreum Min, Cheol Joo Moon, Siriporn Jungsuttiwong et Myong Yong Choi. « Mitigating Intraphase Catalytic‐Domain Transfer via CO2 Laser for Enhanced Nitrate‐to‐Ammonia Electroconversion and Zn‐Nitrate Battery Behavior ». Angewandte Chemie International Edition, 13 août 2024. http://dx.doi.org/10.1002/anie.202413774.
Texte intégralRésumé :
Developing sustainable energy solutions is critical for addressing the dual challenges of energy demand and environmental impact. In this study, a zinc‐nitrate (Zn‐NO3−) battery system was designed for the simultaneous production of ammonia (NH3) via the electrocatalytic NO3− reduction reaction (NO3RR) and electricity generation. Continuous wave CO2 laser irradiation yielded precisely controlled CoFe2O4@nitrogen‐doped carbon (CoFe2O4@NC) hollow nanocubes from CoFe Prussian blue analogs (CoFe‐PBA) as the integral electrocatalyst for NO3RR in 1.0‐M KOH, achieving a remarkable NH3 production rate of 10.9 mgh−1cm−2 at −0.47 V versus RHE with exceptional stability. In‐situ and ex‐situ methods revealed that the CoFe2O4@NC surface transformed into high‐valent Fe/CoOOH active‐species, optimizing the adsorption energy of NO3RR (*NO2 and *NO species) intermediates. Furthermore, DFT calculations validated the possible NO3RR pathway on CoFe2O4@NC starting with NO3− conversion to *NO2 intermediates, followed by reduction to *NO. Subsequent protonation forms the *NH and *NH2 species, leading to NH3 formation via final protonation. The Zn‐NO3− battery utilizing the CoFe2O4@NC cathode exhibits dual functionality by generating electricity with a stable open‐circuit voltage of 1.38‐V versus Zn/Zn2+ and producing NH3. This study inspires the simple design of low‐cost catalysts for NO3RR‐to‐NH3 conversion and positions the Zn‐NO3− battery as a promising technology for industrial applications.